The present invention provides a stuffing box having the self aligning features found in my previous patents, and further includes the improved design of a pressure active seal assembly which adds unexpected long life to the seals thereof as well as affording a unique means of seal adjustment heretofore unknown to those skilled in the art.
In my previous Patent, when pressure set seals are employed, as the rod is reciprocated within the stuffing box, ambient pressure is effected against the uppermost seal of the pack while the lube oil chamber pressure is effected against the lowermost seal pack thereof. Where pressure set seals are employed, the lips of the seals are always set such that the lube oil is wiped from the rod surface on the upstroke with the residual lube oil providing the proper desired amount of lubricant on the downstroke, and this action results in elongated seal life.
Hydraulically set seals, also referred to as pressure set seals, are quite different from compression set seals; namely, the former are not adjusted after installation and therefore changing the seal chamber depth does not improve its seal characteristics, while changing the seal chamber depth of the latter greatly improves its seal characteristics.
Consequently, in my previous inventions, it was found advantageous to employ dual seal packs wherein an upper seal is pressure set while the lower seal is compression set. Accordingly, as the lower compression set seal pack wears, it was desirable to be able to periodically adjust the worn lower seal pack without having to disturb or adjust the upper hydraulic set seal pack, which until now has been captured in an optimunly adjusted manner.
In my previous invention, the tubing pressure on high pressure wells that employ pumpjack units can reach 1000 pounds per square inch, which presents several problems. A major problem is the pressure differential effected across the seal assembly forcing the lower seal flange to be lifted or moved uphole and thereby allowing production fluid to flow into the oil reservoir, thus depleting the lubrication supply. Another problem that sometime occurs in high pressure wells is the great torque required to tighten the closure member of the box against the upthrust of the tubing pressure under these operative conditions. Further, there is a problem of selecting the proper torque value for the closure member in order to properly space out the seal assembly components respective to a satisfactory sealed engagement with respect to the stuffing box roof and floor. These and other problems are overcome by the present invention which uses the pressure differential across the seal assembly to great advantage.
In the various embodiments of this invention, either of a pressure set or compression set seal means can be used advantageously, or a combination thereof, the seal pack of the seal assembly. Therefore, many unforeseen advantages are realized when either a pressure set or a compression set seal pack is employed in accordance with the present invention. In this instance, the compressive force presented by the well tubing pressure is exerted on the seal pack on both the upstroke and downstroke of the pumpjack unit, and as long as the proper compressive forces are effected across the opposed faces of the seal pack, the stuffing box will enjoy an unusually long life, and the seal pack will prevent contamination of the environment for a longer time interval before the seal pack fails. Such a desirable improvement is the subject of this invention.